Known peristaltic pumps in medical apparatuses for extracorporeal blood treatment usually comprise a rotor, a pump casing and an elastic hose line arranged between the rotor and the pump casing as a fluid line. The pump casing usually is configured in one piece and, apart from other functions such as e.g. formation of fluid lines and connectors, fixtures for sensors and covering/shielding of particular parts of the pump from the environment, forms a supporting surface for the fluid line. From the state of the art attached blood pump casings are known, for example configured as a separate milled aluminum part or plastic injection molded part and mounted on a housing front of the apparatus.